The latest round of talks between the MTA and LIRR unions ended after less than four hours Tuesday with both sides holding their positions, and the MTA’s chief looking to Congress for a solution.

At the conclusion of the bargaining session, Metropolitan Transportation Authority spokesman Adam Lisberg announced that agency chairman Thomas Prendergast will head to Washington, D.C., Wednesday to talk to congressional members about whether they intend to intervene in the four-year-long labor dispute, which could culminate in a July 20 strike.

Lisberg declined to detail what went on during the negotiation session, which was overseen by members of the National Mediation Board and included a half-dozen Long Island Rail Road union leaders, but indicated both sides stuck with their most recent settlement offers.

The MTA is pushing for a leaner contract, with 17 percent raises spread over seven years and several concessions affecting future workers. Without a settlement, LIRR workers could legally walk off their jobs in less than two weeks.

Further extinguishing hope to avert a strike, Gov. Andrew M. Cuomo indicated Monday that he would not intervene to help broker a deal.